A wide variety of disposable filters or strainers are known for use in various industries. The assignee of this application has long been in the paint strainer business and used disposable strainers in the past of the type illustrated in U.S. Pat. Nos. Des. 208,488, Des. 208,936 and U.S. Pat. No. 3,741,397. The type of disposable strainer disclosed in those patents comprises a strainer body having an apex and defining a plurality of cutouts which are covered by a straining screen which enables straining through a lower portion of the body with support provided by a thin conical body wall. Such strainers in the past have had apexes formed of the body wall with the cutouts being positioned upwardly of the apex probably because it was thought that the additional strength was needed at the apex. On the other hand, strainers for tea and other purposes have been disclosed as in U.S. Pat. No. 752,019 with apex portions formed of strainer material.
There is some difficulty in forming the strainer material in paint strainers with the strainer material at the apex and having sufficient strength to withstand normal usage as in paint straining where heavy viscous materials are processed.
The high speed manufacture of such strainers requires that the body blank and the strainer filter or screen material be positioned at high speed with minimum waste of material. There is some difficulty in folding strainer blanks with apex filtering material while providing a sufficient joint area to maintain the structural strength of the apex filter material. This is due in some part to the fact that the filter material when folded on itself and glued is difficult to adhere. Maximized lengths of seams and overlapped areas should be used in order to provide for good bonding.